Japanese Knotweed is prevalent in many areas of the UK. What should you do if you discover Japanese Knotweed on your property? How do you make sure a property you are buying isn’t affected? Here are some helpful pointers to make sure you are clear on how to handle this inconvenient invader.

What is Japanese Knotweed and why is it such a problem?

When Victorian engineers were designing our railways, they imported Japanese Knotweed into Britain to hide, or possibly even stabilise, railway embankments. Japanese Knotweed is typically known for colonising volcanoes in Japan and is now known to be a significant problem across the country.

It spreads quickly and can grow up to 10cm a day between April and October with the roots extending up to three metres deep and up to seven metres laterally. It is strong enough to crack tarmac, block drains, undermine foundations and invade homes. Its presence can be enough to cut a property’s value by up to 20% or prevent a mortgage lender approving a loan. It is estimated to be the cause of circa £170 million of home repairs every year and the government estimates that the costs of eradicating it across the UK would be £2.6 billion.

How do I identify Japanese Knotweed?

Mature Japanese Knotweed canes can be identified by their distinctive purple speckle and stand as high as three metres tall. This is when they are fully grown by early summer. Towards the end of summer clusters of small white flowers appear, which are loved by insects for their nectar. In Autumn, the leaves wither and fall off and the canes die and go brown. The rhizome is the part of the plant that is submerged under the soil. It has a dark brown bark and under this external layer, is orange or yellow.

How close is it to me?

Five years ago, the Environment Agency commissioned a new app to track Japanese Knotweed, using the crowd-sourcing principle. More than 20,000 people have now downloaded it, and their data has pinpointed over 6,000 knotweed locations. View the full map at http://www.planttracker.org.uk/map/knotweed where you can zoom into your area. So far, the results show a particular concentration in South Wales, Midlands, London, Scotland’s central belt and Cornwall – where the plant was also introduced by Victorians into ornamental gardens.

What should I do if I have Japanese Knotweed on my property?

Japanese Knotweed is extremely difficult to treat because the roots or rhizomes spread rapidly underground and can regenerate from tiny amounts of material. There are strict regulations which control the its disposal. The Knotweed must be treated at the root and by cutting it down.

“Digging it out of the ground can just spread it terribly,” warns Stephen Hodgson, the chief executive of the Property Care Association (PCA).”If you’ve got it in your garden, either leave it alone, or treat it properly.”

The advice is as follows:

Do not try to dig it up: Tiny root fragments can regenerate into another plant

If you cut down the branches, dispose of them on-site. Compost separately, preferably on plastic sheets

Do not take it to your local council dump. It needs specialist waste management

Do not dispose of it in the countryside. This is against the law

Do not spread the soil – earth within seven horizontal metres of a plant can be contaminated

Take advice from the Invasive Non-Native Specialists Association (INNSA) or the Property Care Association (PCA) on local removal contractors. Many treatments don’t work

In an experiment being conducted in South Wales, thousands of plant lice were released in the summer of 2016, in the hopes that they would help destroy some of the knotweed along river banks. Scientists hope the insects, brought from Japan will stunt the super weed, allowing native species to flourish. However, it is still recommended to seek professional advice on how to eradicate it to ensure that the plant does not get out of control or spread to adjoining properties. Professional knotweed treatment involves injecting the plant with industrial-strength weed killer -Glyphosate.

David Layland, the joint managing director of Japanese Knotweed Control, based in Stockport, says it is the only thing that works. “Once we inject into it, it transfers into the root system pretty quickly, and then it binds with the roots. Over time, it rots away into the subsoil.”

Professional treatment is costly, starting at about £2,500, and going upwards to £30,000 for a major infestation.

Am I liable for knotweed spreading to adjoining properties?

You must deal with Japanese Knotweed straight away. If you fail to do so, then you could be faced with a substantial claim from any adjoining landowner. This claim could be not just for the costs of removing the knotweed from the adjoining property but also for the decrease in value of the adjoining property.

In the recent case of Smith v Line where knotweed was found by the Smiths on property they had acquired from Ms Line. When they discovered the knotweed, the Smiths acted to remove the knotweed from their land and, having successfully eradicated it from their property, requested Ms Line to take action to prevent it spreading back onto their property as it was growing close to the boundary. Ms Line refused, and the judge granted an injunction requiring Ms Line to get a reputable contractor to treat the knotweed on her land and ordered her to pay the Smiths’ costs.

Similarly, in the case Williams v Network Rail, two homeowners in South Wales were awarded £15,000 to compensate them for knotweed which had spread into their gardens.

These cases highlight the possibility of further claims being made more frequently in the future.

What should I do if I am buying a property?

Where sellers of existing properties are aware that the property or garden is, or has been, affected by Japanese Knotweed, they must declare it on the property information form (known as a Form TA6) as part of the conveyancing process. However, developers and builders are not obliged to complete this property information form and if you are buying from a developer or builder then you should make sure your solicitor requests specific enquiries are written to confirm both the current and the historic knotweed position. A buyer should always get a survey of the property carried out and should ensure that the survey includes the garden and, where possible, gardens of adjoining properties.

Can I get insurance against Japanese Knotweed?

Whilst most buildings insurers don’t ask about Japanese Knotweed, they may not cover any treatment so check your buildings insurance policy carefully to see if it is covered. A mortgage lender may also not be willing to lend if the buildings insurance policy won’t cover knotweed.

Indemnity insurance cover can be taken out to provide protection for buyers and mortgage lenders if Japanese Knotweed is discovered. This will generally only be available if no knotweed has been discovered on your property or if it has been successfully treated in the past. This insurance could cover the cost of a survey report to confirm the presence of knotweed, the cost of treatment, repair of any damage caused and could also extend to defending any legal proceedings in the event of any third party being affected.

Privacy Overview

This website uses cookies so that we can provide you with the best user experience possible. Cookie information is stored in your browser and performs functions such as recognising you when you return to our website and helping our team to understand which sections of the website you find most interesting and useful.

Strictly Necessary Cookies

Strictly Necessary Cookie should be enabled at all times so that we can save your preferences for cookie settings.